Wireless communication over relatively short distances is a common and increasingly important feature of electronic devices. In some cases, for example, an electronic device or other appliance is controlled by another electronic device which must communicate instructions to the controlled device (and perhaps receive information from the controlled device). Examples include computer input devices such as mice. Among other advantages, wirelessly transmitting data and/or control signals between a computer and a mouse can dramatically increase user convenience and reduce clutter from multiple connecting cables.
An inherent challenge with wireless devices such as computer mice is power management. Wireless devices are usually battery powered. To prolong battery life, it is desirable to reduce the device's power consumption as much as possible. Many wireless mice utilize an optical tracking system to determine mouse movement. By creating and correlating overlapping images of the surface across which a mouse moves, the mouse “navigates,” i.e., measures relative motion across that surface. Although a significant advancement, the imaging components necessary for optical tracking consume a substantial amount of power. For example, existing CMOS technology used in some imagers requires an extraordinarily bright light source to illuminate the imaged region. This light source (typically a LED) draws a substantial amount of current when illuminated, and is often activated at relatively high rates (1500 frames per second or higher). When activated at a high rate for prolonged periods, the light source (as well as the processing electronics) exhibit a significant drain on battery power.